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Multibody Dynamics Module

Multibody Dynamics Module

Software for Analyzing Assemblies of Rigid and Flexible Bodies

Analysis of the swashplate mechanism to control orientation of helicopter rotor blades. Transient simulation with both rigid and flexible blade designs provides insight into useful performance metrics such as blade deformation and lift force.

Tools for Designing and Optimizing Multibody Systems

The Multibody Dynamics Module is an expansion of the Structural Mechanics Module that provides an advanced set of tools for designing and optimizing multibody structural mechanics systems using finite element analysis (FEA). The module enables you to simulate mixed systems of flexible and rigid bodies, where each body may be subjected to large rotational or translational displacements. Such analyses help identify critical points in your multibody systems, thus enabling you to perform more detailed component-level structural analyses. The Multibody Dynamics Module also gives you the freedom to analyze forces experienced by segments of the structure, and stresses generated in flexible components that may lead to failure due to large deformation or fatigue.

Utilize a Library of Joints

A library of predefined joints is included in the module so that you can easily and robustly specify the relationships between different components of a multibody system, where the components are interconnected such that only a certain type of motion is allowed between them. Joints connect two components through attachments, where one component moves independently in space while the other is constrained to follow a particular motion, depending on the joint type. The joint types in the Multibody Dynamics Module are generic to the extent that they can model any type of connection. Researchers and engineers can thereby design accurate multibody structural mechanics models, using the following joint types:

Prismatic (3D, 2D)

Hinge (3D, 2D)

Cylindrical (3D)

Screw (3D)

Planar (3D)

Ball (3D)

Slot (3D)

Reduced Slot (3D, 2D)

Fixed Joint (2D,3D)

Distance Joint (2D,3D)

Universal Joint (3D)

Additional images:

Orientation of movement for the prismatic, hinge, cylindrical, and screw joints.

Orientation of movement for the planar, ball, slot, and reduced slot joints.

Model of a truck crane used for handling large loads. The simulation analyzes rigid body movement and predicts forces on the crane's axles and hydraulic cylinders. Results are used to optimize the position of link mechanisms in the base.

A swashplate mechanism is used to control the orientation of helicopter rotor blades. This example shows an application derived from the model where only the pitch of the blades can be changed, but where both transient and eigenfrequency analyses can be presented.

Model of a three-cylinder reciprocating engine, having both rigid and flexible parts, is used for maximizing the engine power and the design of structural components.

Complete Flexibility in Analyzing Multibodies

Components of a system that undergo deformations can be modeled as flexible, while other components, or even parts of these components, can
be specified as rigid. You can also provide your multibody dynamics design and analyses with nonlinear material properties by combining models
in the Multibody Dynamics Module with either the Nonlinear Structural Materials Module or the Geomechanics Module. At the same time, the rest of the physics that you can model with COMSOL Multiphysics and the suite of application-specific modules, can be coupled to the physics described by the Multibody Dynamics Module, such as the effects of heat transfer or electrical phenomena.

Transient, frequency-domain, eigenfrequency, and stationary multibody dynamics analyses can be performed. Joints can be assigned linear/torsional
springs with damping properties, applied forces and moments, and prescribed motion as a function of time. Analysis and postprocessing capabilities include:

Relative displacement/rotation between two components and their velocities

Reaction forces and moments at a joint

Local and global coordinate system frames of reference

Stresses and deformations in flexible bodies

Fatigue analysis of critical flexible bodies by combining with the Fatigue Module

Often, motion between two components is restricted due to the presence or functions of other physical objects. Limiting and conditionally locking the
relative motion can be specified for the joints in order to fully define and model these complex systems. In robotics, for example, the relative motion
between two arms can be defined as a pre-defined function of time. Joints can also be spring-loaded and appropriate damping factors can be included in
the Multibody Dynamics Module.

Multibody Dynamics Module

Product Features

Joints can be constrained to restrict the relative motion between the two connected components

Joints can be locked to freeze the relative motion between the two connected components at the specified value

Spring conditions can be applied on the relative motion at a joint, either at the equilibrium or with pre-deformation

Damping or dashpot conditions can be defined to specify losses on the relative motion at a joint

Joints can be required to prescribe the relative motion between the connected components

Frictional loss to a joint can be added for the joint types: Prismatic, Hinge, Cylindrical, Screw, Planar, and Ball.

Forces and moments can be applied to all types of joints at the attachments to the components

Mechanisms can be initialized to translate and rotate rigidly with the given velocities about the specified center of rotation

Application Areas

Aerospace

Automotive

Engine dynamics

Mechatronics

Robotics

Biomechanics

Biomedical instruments

Vehicle dynamics

General dynamic simulations of mechanical assemblies

Performing a Multibody Analysis on a Double Pendulum

You can perform a multibody dynamics simulation to determine the kinematics and dynamics of objects, such as displacement, velocity, and reaction forces.

In this step-by-step instructional video, you will learn how COMSOL Multiphysics together with the Multibody Dynamics Module allow you to perform a flexible multibody analysis (i.e.,model moving parts) on a double pendulum.

You can perform a multibody analysis to determine the kinematics and dynamics of objects, such as displacement, velocity, and reaction forces.
In this step-by-step instructional video, you will learn how COMSOL Multiphysics together with the Multibody Dynamics Module allow you to perform a flexible multibody analysis (i.e., model moving parts) on a double pendulum.
Build the model presented here yourself, by visiting our Model Gallery.

Multibody Dynamics Module

Three-Cylinder Reciprocating Engine

In this example, a dynamic analysis of a three-cylinder reciprocating engine is performed to investigate stresses generated during operation, thereby permitting identification of the critical components. Demand for high power output relative to the weight of the engine requires careful design of its components.
This model of a reciprocating ...

Helicopter Swashplate Mechanism

This model illustrates the operation of a swashplate mechanism used in helicopters to translate the input of helicopter flight control into the motion of the rotor blades, and hence controls the orientation of the rotor blades.
In this model, the rotor blades are modeled as either rigid bodies or flexible bodies in two different cases. All other ...

Dynamics of a Double Pendulum

This is a tutorial model that shows how to model a hinge joint and use additional functionality including constraints, locking, spring-damper and prescribed motion.
The model illustrates the nonlinear dynamics of the double pendulum. Locus of the tip of the lower arm and the phase space curve are plotted to demonstrate the chaotic behavior ...

Mechanical Assembly with Hinge Joint

This example illustrates how to model a barrel hinge connecting two solid objects in an assembly. In this model, the details of the connection are not the focus of the analysis, therefore, the hinge joint is modeled using a Joint feature in the Multibody Dynamics Module. The connected parts can be either rigid or flexible or a combination as shown ...

Spring Loaded Centrifugal Governor

A centrifugal governor is used to control the speed of rotating machinery. One of the most common applications is in controlling the RPM of an engine by regulating the fuel supply.
This model illustrates the functioning of a spring loaded centrifugal governor. The dynamics of the governor are analyzed under the influence of a centrifugal ...

Stresses and Heat Generation in a Landing Gear Mechanism

This model simulates the dynamics of the shock absorber used in a landing gear mechanism of an aircraft.
It analyses the stresses, as well as the heat generated in the landing gear components due to the energy dissipated in the shock absorber. A prismatic joint, with spring and damper, is used to model the shock absorber assembly.

Slider Crank Mechanism

This is a benchmark model to test the numerical algorithms in the area of multibody dynamics.
This model simulates the dynamic behavior of the slider crank mechanism. This mechanism goes through singular positions during its operation. The acceleration at a point is compared with the results from the reference.

Modeling Gyroscopic Effect

Gyroscopes are used for measuring the orientation or maintaining the stability of airplanes, spacecraft, and submarines vehicles in general. They are also used as sensors in inertial guidance systems.
This model demonstrates the modeling of a mechanical gyroscope. It analyzes the response of the spinning disc to an external torque coming on the ...

Shift into gear

This model demonstrates the ability to simulate Multibody Dynamics in COMSOL. It comprises a multilink mechanism that is used in an antique automobile as a gearshift lever. It was created out of curiosity to find out how large forces are on the individual components. The model uses flexible parts, i.e. the Structural Mechanics Module was used ...

Dynamic Behavior of a Spring Loaded Rotating Slider

This model illustrates the modeling of slider motion caused by a base rotation. The motion of the slider is analyzed under various forces such as inertia force, centrifugal force, spring force and damping force.
The prismatic joint, which is used to connect the two components, is spring loaded and also includes damping effects.
The motion of ...

Spring Loaded Centrifugal Governor

Stresses and Heat Generation in a Landing Gear Mechanism

Slider Crank Mechanism

Modeling Gyroscopic Effect

Shift into gear

Dynamic Behavior of a Spring Loaded Rotating Slider

Three-Cylinder Reciprocating Engine

In this example, a dynamic analysis of a three-cylinder reciprocating engine is performed to investigate stresses generated during operation, thereby permitting identification of the critical components. Demand for high power output relative to the weight of the engine requires careful design of its components.
This model of a reciprocating ...

Helicopter Swashplate Mechanism

This model illustrates the operation of a swashplate mechanism used in helicopters to translate the input of helicopter flight control into the motion of the rotor blades, and hence controls the orientation of the rotor blades.
In this model, the rotor blades are modeled as either rigid bodies or flexible bodies in two different cases. All other ...

Dynamics of a Double Pendulum

This is a tutorial model that shows how to model a hinge joint and use additional functionality including constraints, locking, spring-damper and prescribed motion.
The model illustrates the nonlinear dynamics of the double pendulum. Locus of the tip of the lower arm and the phase space curve are plotted to demonstrate the chaotic behavior ...

Mechanical Assembly with Hinge Joint

This example illustrates how to model a barrel hinge connecting two solid objects in an assembly. In this model, the details of the connection are not the focus of the analysis, therefore, the hinge joint is modeled using a Joint feature in the Multibody Dynamics Module. The connected parts can be either rigid or flexible or a combination as shown ...

Spring Loaded Centrifugal Governor

A centrifugal governor is used to control the speed of rotating machinery. One of the most common applications is in controlling the RPM of an engine by regulating the fuel supply.
This model illustrates the functioning of a spring loaded centrifugal governor. The dynamics of the governor are analyzed under the influence of a centrifugal ...

Stresses and Heat Generation in a Landing Gear Mechanism

This model simulates the dynamics of the shock absorber used in a landing gear mechanism of an aircraft.
It analyses the stresses, as well as the heat generated in the landing gear components due to the energy dissipated in the shock absorber. A prismatic joint, with spring and damper, is used to model the shock absorber assembly.

Slider Crank Mechanism

This is a benchmark model to test the numerical algorithms in the area of multibody dynamics.
This model simulates the dynamic behavior of the slider crank mechanism. This mechanism goes through singular positions during its operation. The acceleration at a point is compared with the results from the reference.

Modeling Gyroscopic Effect

Gyroscopes are used for measuring the orientation or maintaining the stability of airplanes, spacecraft, and submarines vehicles in general. They are also used as sensors in inertial guidance systems.
This model demonstrates the modeling of a mechanical gyroscope. It analyzes the response of the spinning disc to an external torque coming on the ...

Shift into gear

This model demonstrates the ability to simulate Multibody Dynamics in COMSOL. It comprises a multilink mechanism that is used in an antique automobile as a gearshift lever. It was created out of curiosity to find out how large forces are on the individual components. The model uses flexible parts, i.e. the Structural Mechanics Module was used ...

Dynamic Behavior of a Spring Loaded Rotating Slider

This model illustrates the modeling of slider motion caused by a base rotation. The motion of the slider is analyzed under various forces such as inertia force, centrifugal force, spring force and damping force.
The prismatic joint, which is used to connect the two components, is spring loaded and also includes damping effects.
The motion of ...